Which of the following explains why a small conflict in the Balkans spread to all of Europe? A. Many of the European powers had entered into alliances requiring them to defend each other.
B. Most of the European powers lacked military defenses to stop an attack.
C. Serbia refused all of Austria-Hungary’s demands, prompting other nations to declare war.
D. Slavs in Russia refused to support their fellow Slavs in the Balkan region.